Lift



| F. JAsEPH 2,25%@9 LIFT A Filed Sept. 23, 1940 2 Sheets-Sheet 2 ,e0 A u72O O Patented Sept. 2, 1941 LIFT Lawrence F. Jaseph, Memphis, Tenn.,assignor to Rotary Lift Company, Memphis, Tenn., a corporation ofDelaware Application September 23, 1940, Serial No. 357,849

4 Claims.

This invention relates to lifts.

It will be explained as embodied in a lift particularly adapted for theelevation of automobiles for underbody servicing.

In lifts of the type frequently referred to as air-hydraulic orsemi-hydraulic, the plunger as well as the cylinder serves as areservoir for oil. To raise the lift, air pressure is applied to theinterior of the plunger above the oil level and as the plunger. rises,oil ows therefrom through 'a restricted passage into the chamber formedbetween the stationary cylinder and the movable plunger. To lower thelift, the air pressure is released from the interior of the plunger and.under the influence of the weight of the descending plunger and itsload, the oil is forced back from the cylinder through the restrictedpassage into the plunger. In such lifts an air pocket tends to form inthe space between the plunger and the cylinder between the upper levelof the oil and the packing at the top of the cylinder. Because ofseepage of air into this pocket during operations of the lift, thepocket tends to become larger with the result that unsatisfactoryoperation and loss of oil may result.

In orderl to overcome this diiilculty, it has been common practice toprovide an external manually operated vent for the air pocket, the ventbeing normally closed by suitable means, such as a plug. Frequently,however, installers and cperators neglect to vent the air pocket withthe result that unsatisfactory operation of the lift, as well as loss ofoil therefrom may take place, as mentioned heretofore.

The object of my invention is to provide an automatic air bleeder whichwill prevent the formation of objectionable air pockets in lifts.

A further object is to provide an automatic air bleeder, integral withthe mechanism, which will allow the unwanted air in the lift to escapeeach time the lift is operated.

A further object is to provide a bleeder which will automaticallyexhaust the air in the lift both at the time of the initial operation ofthe lift, and at all times thereafter.

Another object is to provide an automatic air bleeder which may be usedwith a combination air and hydraulic lift.

A further object is to provide a lift which will operate accurately,smoothly, safely, and economically with a minimum amount of attention onthe part of the operator.

Another object is to provide an automatic bleeder for lifts which issimple in construction and operation and whichis economical tomanufacture.

Other objects, advantages, and capabilities of the invention will appearfrom the following description of preferred embodiments thereof, takenin conjunction with the accompanying drawings, in which similar numeralsrefer to similar parts.

In the drawings: 4

Fig. 1 is a vertical section of a lift showing one arrangement of ableeder pipe to vent automatically the air pocket below the packing, and

Fig. 2 is a vertical section of a modified arrangement for accomplishingthis end.

Referring first to Fig. 1, the lift includes a cylinder or outsidecasing 5 sealed at the lower end and open at the top. Usually, asindicated, the cylinder is embedded in the ground with its upper openend slightly below the level of thev ground or garage floor. Slidablyarranged within the cylinder is a hollow piston or plunger 6, whichcarries the automobile supporting superstructure. In order to maintainan air-tight seal between the plunger and the open end of the cylinder,conventional packing 'l and an adjustable gland 8 are employed. Byreference to the drawings it may be seen that the plunger-is tightlysealed at its upper end by means of a piston head I2 which is drilledand tapped to receive a threaded air-tight fill-plug I3.

An air line I6, open at its upper end, enters the cylinder by means ofan air-tight elbow I1, and extends loosely through an orice I5 in thelower head Ill of the plunger, to a point somewhat below the upperplunger head I2 when the plunger is in its lowermost position, as shownby the dotted lines. Preferably the orice I5 is larger than the air lineI6 by an amount which will produce a safe and proper lowering speed withthe air pressure released by restricting the ow of oil-or otherliquid-from the cylinder to the plunger during descent of the plunger.If desired, a differential valve may be employed to vary the size of theeiective liquid passage between cylinder and plunger when the plunger iselevated and when it descends, such, for example, as set forth in UnitedStates Patent No. 1,689,145 to Lunati.

In order tohold rigidly the plunger 6 as it rises and falls within thecylinder 5, there is provided a bearing cage I8 which is securelyfastened to the interior of the cylinder by means of an annular collarI9, as well as by means of bolts 20 at the upper flange of the bearingcage. The upward movement of the plunger is limited by a stop-ring 2lwhich is adapted to engage a bearing 21 at the lower extremity of thebearing ca e.

in automatic bleeder pipe 22, disposed vertically within the plunger 3,passes through the wall of the plunger at a point below the pack-`ing,preferably immediately below an upper bearing 28 in the lbearingcage I8 when the plunger is ln a fully or nearly fully raised position.The lower` end of the bleeder pipe 22 is open, and extends to a pointlslightly above the lower plunger head Il of the plunger 5.

To make certain that the air in the space between the plunger 6 and thecylinder 5 will be entirely exhausted by the action of the bleeder pipe22, a plurality of holes 23 are drilled throughout the circumference ofthe 4bearing cage I8 to permit the level of the oil to equalize insideand outside the bearing cage.

'Ihe initial installation and operation of the lift is as follows: Afterthe parts have been assembled the plunger 6 will be at rest upon theblocks 24 at the bottom of the cylinder, as is shown by the dottedlines. The lift is then filled with oil up to the point somewhat belowthe open end of the inside air line I 6, and the ull-plug I3 is screwedinto place. Air pressure is supplied by a compressor or other suitablesource connected to an exterior air line 25 by means of an elbow 26. Asthe plunger 3 rises, impelled by the increased pressure within it. theoil will flow through the orice l into the outer cylinder 5. Naturally,the air pressure within the plunger will be exerted equally in alldirections, so that the same force which is exerted against the interiorof the plunger to force it upward is likewise exerted against thesurface of the oil. As the plunger rises, the pressure of the air uponthe surface of the oil within the plunger will cause the oil in thecylinder to rise into the space or "pocket between the plunger 6 and thecylinder 5 between the packing 1 and the lower bearing ring 21,compressing any air trapped therein. The pressure within this pocketwill be somewhat lower than the pressure required within the plunger toraise the plunger and its load.

When the plunger reaches its fully raised position, as shown by theheavy lines in Fig. 1, the upper opening of the bleeder pipe 22 is abovethe oil level, while the lower opening of the bleeder pipe extends belowthe surface of the oil.

The bleeding operation of this embodiment is accomplished as follows:When the air pressure within the plunger is released and the plungerdescends. a differential between the pressure within the plunger andwithin the cylinder outside of the plunger exists-the pressure on theoutside of the plunger being greater than that within the plunger.'I'his differential in pressure causes air, if any be present in thespace or pocket" between the plunger 6 and cylinder 5 above the lowerbearing ring 21, to flow through the bleeder pipe 22 into the plunger.Air flow through the bleeder pipe 22 continues during lowering of theplunger and, because of the slight viscosity and density of air, aconsiderable volume of air will pass through the bleeder pipe 22 in ashort time.A And as the air passes through the bleeder pipe into theplunger, oil rises to take its place in the pocket. The first time thelift is operated after being filled with oil, the oil level will dropequal to the volume required to fill the air pocket between the plunger6 and the cylinder 5 between the packing 1 and the lower bearing ring21. It may be desirable, therefore,

to add oil after the first few operations in order to establish theproper operating level.

Referring now to Fig. 2, it will be observed that another embodiment ofthe invention is illustrated, wherein a bleeder pipe 3| is used inconjunction with a valve 30 to accomplish the automatic bleedingoperation. This valve consists of a housing 32, a valve seat 33, amovable ball 34, and a retaining pin 35. The bleeder pipe is arrangedwithin the plunger S and passes through the wall of the plunger at apoint which will be below the packing-preferably immediately below theupper bearing 28 in the bearing cage i8 when the plunger is in a fullyor nearly fully raised position.

The operation of this embodiment of the bleeder pipe is as follows: Whenthe air pressure within the plunger 6 is released and the plunger is a1-lowed to descend, the pressure within the plunger will necessarilydecrease more rapidly than the pressure in the air pocket for thereasons already stated. This difference in pressure causes air, if anybe present in the space or pocket between the plunger 6 and the cylinder5 above the lower bearing ring 21, to flow through the bleeder pipe 3|,to unseat the ball 3l, and to ilow into the plunger 6. The ball 3| isprevented from leaving the valve assembly entirely by means of theretaining pin 35.

On the other hand, when the pressure in the space between the plunger 6and the cylinder 5 between the packing 1 and the lower bearing ring 2lis less than the pressure within the plunger I. as during upward travelof the plunger, the ball 34 will close against the valve seat 33 becauseof the greater pressure within the plunger. When the ball is in thisposition air from within the plunger cannot enter the space between theplunger and the cylinder, and thus the air pocket is prevented fromre-forming after being eliminated. The bleeder pipe with the valve 30works equally well whether it is above or below the level of the oil.

0f course, the action of both embodiments of the bleeder pipe isentirely automatic, so that every time the lift is operated, the airthat would ordinarily accumulate will be disposed of. as described,simply by the raising and lowering of the plunger, and without anyeffort on the part of the operator.

Although this invention has been described in connection with certainspecific embodiments, the principles involved are susceptible ofnumerous other applications that will readily occur to persons skilledin the art. 'I'he invention is, therefore, to be limited only by thescope of the appended claims.

Having thus described the various features of the invention, what Iclaim as new and desire to secure by United States Letters Patent is:

l. A lift of the type having a relatively movable cylinder and plungerwith fluid-tight packing therebetween and wherein air pressure releasedwithin the plunger above the level of a liquid contained therein exertsupward pressure on the plunger and downward pressure on the liquid toelevate the plunger and force the liquid from the plunger through arestricted passage into the cylinder, characterized by an air bleederpipe opening at one end through the wall of the plunger at a point belowthe packing when the plunger is fully elevated and opening at the otherend within the plunger.

2. A lift of the type having a relatively movable cylinder and plungerwith fluid-tight packing therebetween and wherein air pressure releasedwithin the plunger above the level of a. liquid cont tained thereinexerts upward pressure on the plunger and downward pressure on theliquid to elevate the plunger and force the liquid from the plungerthrough a restricted passage in-to the cylinder, characterized by an airbleeder pipe opening at one end through the wall of the plunger at apoint below the packing when the plunger is fully elevated and openingat the other end below the level of the liquid in the plunger.

3. In a lift, the combination of a cylinder open at one end and closedat the other end, a hollow plunger slidably mounted in the cylinder, theupper end of the plunger being closed and the lower end having arestricted passage into the cylinder, uid presure-tight packing betweenthe cylinder and plunger, a liquid partly filling the cylinder andplunger, an air pressure inlet opening into the plunger above the oillevel therein,

the air pressure acting upwardly on the upper closed plunger head anddownwardly upon the liquid to elevate the plunger andforce liquid fromthe plunger through the restricted passage into the cylinder, and an airbleeder passage extending through the wall of the plunger at a pointslightly below the packing when the plunger is fully elevated andextending to a point below the liquid level in the plunger to permit theescape of air trapped between the plunger and cylinder when air pressureis released from the plunger.

4. A lift of the type having a relatively movable cylinder and plungerwith uid-tight packing therebetween and wherein air pressure releasedwithin the plunger above the level of a liquid contained therein exertsupward pressure on the plunger and downward pressure on the liquid toelevate the plunger and force the liquid from the plunger through arestricted passage into' the cylinder, characterized by a bleeder pipewithin the plunger opening at one end through the wall of the plunger ata point below the packing when the plunger is fully elevated, and acheck valve in said bleeder pipe for arresting the flow of iluid fromthe inside to the outside of the plunger, while permitting the ow of uidfrom the outside to the inside of the plunger.

LAWRENCE F. JASEPH.

